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Ecology and the Biosphere. Chapter 50. Ecology - the study of the interactions between organisms and their environments. The interactions between organisms and their environments determine their distributions and abundances. Distribution = geographic range abundance=individuals per unit area
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Ecology and the Biosphere Chapter 50
Ecology - the study of the interactions between organisms and their environments
The interactions between organisms and their environments determine their distributions and abundances • Distribution = geographic range • abundance=individuals per unit area • environmental factors • abiotic - non-living chemical and physical factors • biotic - living factors like other organisms
Figure 50.1 Distribution and abundance of the red kangaroo in Australia, based on aerial surveys
Examples of ecological questions: • How do diving whales select their feeding areas? • What processes recycle vital chemical elements, such as nitrogen, in a savanna ecosystem • What factors influence the diversity of tree species that make up a particular forest
Factors affecting the distribution of organisms • dispersal • behavior and habitat selection • biotic factors • abiotic factors
Biogeography • The study of past and present distributions of individual species • continental drift and barriers contribute to distinctive floras and faunas of the Earth’s major regions
Dispersal • Example: Kangaroos may not be in North America because they historically had no way of getting there. • To test this: species transplant experiments
Figure 50.6 Set of transplant experiments for a hypothetical species
Transplant successful - distribution limited because of dispersal problems • inaccessible, not enough time to reach area, not recognized as suitable living space • transplant unsuccessful - distribution limited by biotic or abiotic factors, I.e., for some reason cannot survive there.
Invasive species • In modern times, normal restrictions on dispersal are lifted and invasive species can proliferate
Figure 50.7 Spread of the African honeybee in the Americas since 1956
Figure 50.8 Expansion of the geographic range of the zebra mussel (Dreissenapolymorpha) since its discovery near Detroit in 1988
Spartina alterniflora and Spartina anglica • Saltmarsh grasses native to the Eastern U.S. (S. alterniflora) and British Isles (S. anglica). • Invasive species in Puget Sound and Willapa Bay in Washington State.
Spartina are physiologically resilient and vigorous • Physiological tolerance • Wide range of salinities • Waterlogged soils • Anoxia • Hydrogen sulfide • Fast rate of spread - average 10-20% per year (can be much greater)
Willapa Bay • Spartina alterniflora • 10,000 to 25,000 acres affected • Nearly 4000 solid acres
Puget Sound • Spartina anglica • ≈7000 acres affected • Solid acres: • Pink=<1 • Peach= 1-5 • Blue=6-100 • Red=>100 1999
Managing the spartina problem • >$10 million spent since 1990 • Affected areas have increased from a few thousand to >20,000 acres • Herbicide and mechanical control • $2000 per acre per year
Distribution of hydrogen sulfide in sediments Oxidized zone No hydrogen sulfide Anoxic zone Hydrogen sulfide-rich
Tolerating anoxic sediments • Aerenchyma • Anaerobic metabolism • Alcohol dehydrogenase • Sulfide oxidation Spartina anglica root
Biotic factors affect the distribution of organisms • Competition • interspecific • intraspecific • Predation • Mutualism - species helping each other
Limpet and urchin removal experiments • Results show that the herbivores limit the distribution and abundance of seaweed • limpets appear to be the main herbivores • but why is there more seaweed when both limpets and urchins are removed?
Temperature and water are major climatic factors determining the distributions of organisms • Biome-a major type of ecosystem
Figure 50.10 A climograph for some major kinds of ecosystems (biomes) in North America
Figure 50.15 Lake stratification and seasonal turnover (Layer 1) • Winter • cold water at surface • warmer deeper in lake
Spring - surface water warms and sinks allowing mixing. Oxygen to bottom waters and nutrients to surface waters
summer • Thermal profile develops • thermocline -separates cold bottom water and warm surface water
Figure 50.15 Lake stratification and seasonal turnover (Layer 4)
Fall • Surface water cools rapidly and sinks • thermocline disappears • remixing of lake water
Figure 50.16 Current geographic range and predicted future range for the American beech (Fagusgrandifolia) under two climate-change scenarios
Figure 50.19 Freshwater biomes: Oligotrophic lake (left), eutrophic lake (top right), stream flowing into a river (bottom right)
